The invention relates to a remelting furnace having a crucible and a sealed pot placed thereon which is removable from the crucible by a lifter, and having a stuffing box through which an electrode rod serving to hold a consumable electrode passes. The stuffing box is held by a bottom platform suspended on rods from a weighing platform supported by weighing cells on a frame. The electrode rod can be raised and lowered in order to control the melting, and it is held with its electrode driver by the weighing platform.
Remelting furnaces of the above kind are generally known and serve for the production of high-quality metal alloys by the electrical remelting of an electrode in a vacuum by the VAR process. In such remelting furnaces it is necessary to control with the greatest possible accuracy the rate at which the electrode melts, and to feed the electrode rod continuously into the crucible during the melting so that, despite the melting and the rise of the molten metal in the crucible, it will always reach sufficiently far into the crucible. To be able to move the electrode rod into the crucible always to the desired extent, the electrode rod is supported on weighing cells on a weighing platform, so that the weight of the electrode fastened to it can be determined continuously. The bottom platform with the stuffing box is likewise supported by the weighing platform, so that the friction between the electrode rod and the stuffing box will not falsify the weight measurement.
When the crucible is to be recharged, the pot has to be lifted off it by means of the lifter. In the known remelting furnace, the lifter is used to raise an inner frame on which the weighting platform is supported. Thus, when the pot is lifted the entire upper part of the furnace is raised upward with the pot. This increases the structural height of the remelting furnace by the length of movement of the pot, and often this is not possible on account of the overhead crane track which runs above the remelting furnace and is too low to allow this movement. Also, the part of the furnace that has to be lifted is very heavy, so that the lifter must be of sufficiently stable construction and is therefore expensive.
To avoid increasing the structural height, remelting furnaces have been built in which only the pot with the stuffing box is raised instead of the entire upper part of the furnace. To compensate the influence of the friction of the stuffing box on the measured weight of the electrode rod, an additional weight measuring system could be associated with the stuffing box. Such a design would be very complex, however, and therefore it has not been built. In such remelting furnaces, either the friction of the stuffing box was ignored, or else the feed of the electrode rod was controlled not by measuring its weight but by the plunge depth of the electrode rod, i.e., by the change in length of the electrode.